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Interpretive Summary: The addition of milk and milk-based products to poor individuals consuming plant-based diets has been suggested to improve health and nutrition. However, the increased amount of calcium in the diet may impair iron and zinc absorption. We measured iron and zinc absorption in 48 Mexican women consuming three different diets: (1) A typical rural Mexican diet that is high in plant foods, (2) the same diet with added milk, (3) the same diet with added yogurt. Addition of milk or yogurt had no effect on iron absorption. Milk or yogurt decreased the percent iron absorption by 50-68%; however, because the milk and yogurt contained good amounts of zinc, the total amount of zinc absorbed from the meal actually increased (by 70%). Adding milk or yogurt to a plant-based diet did not reduce the amount of iron absorbed, and increased the amount of zinc absorbed. Milk or yogurt can be safely used to improve the nutrtion of poor individuals consuming predominantly plant-based diets.

Technical Abstract: The addition of milk and milk-based products to the diets of individuals subsisting on plant-based diets was reported to have positive effects on nutritional status and functional outcomes such as growth, morbidity, and cognition. We examined the effect of the addition of milk or yogurt on the bioavailability of zinc and iron from a plant-based rural diet. The subjects were 48 Mexican women (30.9 ± 5.7 y) who habitually consumed a plant-based diet. The women were assigned to 1 of 3 groups: 1) the typical rural Mexican diet, 2) that diet with milk added, or 3) that diet with yogurt for 13 d. Zinc absorption was measured after extrinsically labeling meals with 67Zn and an i.v. dose of 70Zn; iron absorption was measured by extrinsically labeling meals with 58Fe and a reference oral dose of 57Fe. Including milk and yogurt in the diet increased zinc absorption by 50 and 68%, respectively (P < 0.05). The 3 groups did not differ in the percentage iron absorption. The total amount of zinc absorbed was increased (P < 0.05) by 70% when milk was added to the meal and 78% when yogurt was added. The total amount of iron absorbed did not differ among the groups. The addition of milk and yogurt to a plant-based diet high in phytate increases zinc bioavailability without affecting iron bioavailability.